The idea behind the game is to find all of the runes and put them in order in the main room. Keys unlock more rooms (a total of 4 rooms: Left, Upper Left, Upper Right, and Right). The hints about the rune order are on the walls in the game. This is told to you when you start the game, as well as in the 1st puzzle room with the boxes when the character sees the wall with 3 runes on it.
Hopefully, this helps you understand it better and have a better experience playing the game!